POST-EXERCISE MUSCLE GLYCOGEN REPLETION IN THE EXTREME: EFFECT OF FOOD ABSENCE AND ACTIVE RECOVERY
Glycogen plays a major role in supporting the energy demands of skeletal muscles during high intensity exercise. Despite its importance, the amount of glycogen stored in skeletal muscles is so small that a large fraction of it can be depleted in response to a single bout of high intensity exercise....
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2004-09-01
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doaj-abb9f695e91342739a79f2345d3e97442020-11-25T02:25:52ZengUniversity of UludagJournal of Sports Science and Medicine1303-29682004-09-0133139146POST-EXERCISE MUSCLE GLYCOGEN REPLETION IN THE EXTREME: EFFECT OF FOOD ABSENCE AND ACTIVE RECOVERY Paul A. FournierTimothy J. FairchildLuis D. FerreiraLambert BräuGlycogen plays a major role in supporting the energy demands of skeletal muscles during high intensity exercise. Despite its importance, the amount of glycogen stored in skeletal muscles is so small that a large fraction of it can be depleted in response to a single bout of high intensity exercise. For this reason, it is generally recommended to ingest food after exercise to replenish rapidly muscle glycogen stores, otherwise one's ability to engage in high intensity activity might be compromised. But what if food is not available? It is now well established that, even in the absence of food intake, skeletal muscles have the capacity to replenish some of their glycogen at the expense of endogenous carbon sources such as lactate. This is facilitated, in part, by the transient dephosphorylation-mediated activation of glycogen synthase and inhibition of glycogen phosphorylase. There is also evidence that muscle glycogen synthesis occurs even under conditions conducive to an increased oxidation of lactate post-exercise, such as during active recovery from high intensity exercise. Indeed, although during active recovery glycogen resynthesis is impaired in skeletal muscle as a whole because of increased lactate oxidation, muscle glycogen stores are replenished in Type IIa and IIb fibers while being broken down in Type I fibers of active muscles. This unique ability of Type II fibers to replenish their glycogen stores during exercise should not come as a surprise given the advantages in maintaining adequate muscle glycogen stores in those fibers that play a major role in fight or flight responseshttp://www20.uludag.edu.tr/%7Ehakan/sbtd/vol3/n3/4/v3n3-4.htmGlycogen synthaseglycogen phosphorylaseCori cycleglyconeogenesis |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Paul A. Fournier Timothy J. Fairchild Luis D. Ferreira Lambert Bräu |
spellingShingle |
Paul A. Fournier Timothy J. Fairchild Luis D. Ferreira Lambert Bräu POST-EXERCISE MUSCLE GLYCOGEN REPLETION IN THE EXTREME: EFFECT OF FOOD ABSENCE AND ACTIVE RECOVERY Journal of Sports Science and Medicine Glycogen synthase glycogen phosphorylase Cori cycle glyconeogenesis |
author_facet |
Paul A. Fournier Timothy J. Fairchild Luis D. Ferreira Lambert Bräu |
author_sort |
Paul A. Fournier |
title |
POST-EXERCISE MUSCLE GLYCOGEN REPLETION IN THE EXTREME: EFFECT OF FOOD ABSENCE AND ACTIVE RECOVERY |
title_short |
POST-EXERCISE MUSCLE GLYCOGEN REPLETION IN THE EXTREME: EFFECT OF FOOD ABSENCE AND ACTIVE RECOVERY |
title_full |
POST-EXERCISE MUSCLE GLYCOGEN REPLETION IN THE EXTREME: EFFECT OF FOOD ABSENCE AND ACTIVE RECOVERY |
title_fullStr |
POST-EXERCISE MUSCLE GLYCOGEN REPLETION IN THE EXTREME: EFFECT OF FOOD ABSENCE AND ACTIVE RECOVERY |
title_full_unstemmed |
POST-EXERCISE MUSCLE GLYCOGEN REPLETION IN THE EXTREME: EFFECT OF FOOD ABSENCE AND ACTIVE RECOVERY |
title_sort |
post-exercise muscle glycogen repletion in the extreme: effect of food absence and active recovery |
publisher |
University of Uludag |
series |
Journal of Sports Science and Medicine |
issn |
1303-2968 |
publishDate |
2004-09-01 |
description |
Glycogen plays a major role in supporting the energy demands of skeletal muscles during high intensity exercise. Despite its importance, the amount of glycogen stored in skeletal muscles is so small that a large fraction of it can be depleted in response to a single bout of high intensity exercise. For this reason, it is generally recommended to ingest food after exercise to replenish rapidly muscle glycogen stores, otherwise one's ability to engage in high intensity activity might be compromised. But what if food is not available? It is now well established that, even in the absence of food intake, skeletal muscles have the capacity to replenish some of their glycogen at the expense of endogenous carbon sources such as lactate. This is facilitated, in part, by the transient dephosphorylation-mediated activation of glycogen synthase and inhibition of glycogen phosphorylase. There is also evidence that muscle glycogen synthesis occurs even under conditions conducive to an increased oxidation of lactate post-exercise, such as during active recovery from high intensity exercise. Indeed, although during active recovery glycogen resynthesis is impaired in skeletal muscle as a whole because of increased lactate oxidation, muscle glycogen stores are replenished in Type IIa and IIb fibers while being broken down in Type I fibers of active muscles. This unique ability of Type II fibers to replenish their glycogen stores during exercise should not come as a surprise given the advantages in maintaining adequate muscle glycogen stores in those fibers that play a major role in fight or flight responses |
topic |
Glycogen synthase glycogen phosphorylase Cori cycle glyconeogenesis |
url |
http://www20.uludag.edu.tr/%7Ehakan/sbtd/vol3/n3/4/v3n3-4.htm |
work_keys_str_mv |
AT paulafournier postexercisemuscleglycogenrepletionintheextremeeffectoffoodabsenceandactiverecovery AT timothyjfairchild postexercisemuscleglycogenrepletionintheextremeeffectoffoodabsenceandactiverecovery AT luisdferreira postexercisemuscleglycogenrepletionintheextremeeffectoffoodabsenceandactiverecovery AT lambertbrau postexercisemuscleglycogenrepletionintheextremeeffectoffoodabsenceandactiverecovery |
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